Wastewater and landfill leachate has been managed and controlled for decades to reduce and help prevent contamination of surrounding soils, waterways, and underground aquifers. Landfills are generally built away from natural habitat and where there is not an underground water source, and are used to discard solid waste materials, including old televisions, computers, telephones, paint cans, motor oil, batteries, electronic devices, and countless other waste materials and substances which are not degradable or recyclable, by burying them in layers in the soil. Besides large economic advantages to be gained, e.g., including from international and municipal sources or entities paying for waste disposal, landfills help minimize environmental harm from these solid wastes and allow waste to decompose under controlled conditions until its eventual transformation into relatively inert, stabilized material.
Landfill leachate is a “toxic soup” of liquid material that drains from a landfill and contains a wide concentration range of undesirable and toxic materials that can be harmful to the environment and health. The leachate consists of many organic and inorganic compounds that may be either dissolved or suspended in the leachate liquid, including, but not limited to, toluene, phenols, benzene, ammonia, dioxins, polychlorinated biphenyls (PCBs), chlorinated pesticides, heavy metals and endocrine-disrupting chemicals. Modern landfills are lined with impermeable layers to prevent leachate from leaking out and contaminating groundwater or surface water of a nearby community. The leachate treatment typically consists of two basic types: biological and physical/chemical. Depending on the treatment goals, sometimes both types are combined. The organic strength of landfill leachate can be greater than 20 to 100 times the strength of raw sewage, which is why the landfills typically have pipes designed to route and collect leachate and have non permeable liners to keep the leachate from contaminating ground water and entering the drinking water in neighborhoods near the landfill.
Landfill leachate is known to be very difficult to treat. One of the main reasons for this is its often changing matrix. The pH can also fluctuate from day-to-day, making it even more difficult to treat. Factors affecting the composition of landfill leachate include: the landfill conditions (climate, pH, temperature, degree of ongoing decomposition, and landfill age); the type of waste discharged to the landfill (biodegradable or non-biodegradable, soluble or insoluble, organic or inorganic, liquid or solid, toxic or nontoxic); the landfill features (size, depth, permeability and soil mineral characteristics under the landfill), and the moisture content of the wastes.
Landfill leachate constitutes a major environmental, economical and social problem worldwide, largely because the waste volume is growing faster than the world's population. Moreover, as stricter environmental requirements are continuously imposed regarding ground and surface waters, the treatment of landfill leachate becomes a major environmental concern.
Magnetic separation for the purpose of cleaning and purifying drinking water is generally known. Also employed is sand clarification for water treatment systems because sand is inexpensive and has a density about two times that of water. This helps to settle the solids of the wastewater, usually in a clarifier. Magnetite, a fully oxidized non-toxic form of iron (Fe3O4) commonly found in the environment, has become an alternative to sand as the ballast of choice because of its inexpensiveness and its five times greater density than water. The magnetite is also ferromagnetic, allowing it to be recovered by rare earth magnets.
Another known method for treating landfill leachate in a 20 foot shipping container is known. The leachate is collected in an equalization tank which is placed underground and just below the 20 foot shipping container which houses the cleaning system. A biological tank and sedimentation tank are also placed underground. After aerating and biologically treating the raw leachate, the leachate is pumped into a flash flocculation (floc) tank inside the shipping container. Inside the shipping container is the flash floc tank, a magnetic separator, chemical feed pumps and a control panel. In this known method the customer was landlocked and had a very limited space to treat their leachate. The system uses magnetic seeding technology with magnetite as the ballast of choice. The leachate water is treated with coagulants, polymers and magnetite in the flash floc tank and then passed through fifteen magnetic disks. This process is not successful and has many disadvantages. The most difficult problem is the amount of solids and the many different types of solids in the leachate which make it practically impossible to precipitate all of the dissolved ions of the leachate and to allow them to clump or floc on a daily basis.
Another problem with this process is that if the leachate in the biological tank is not allowed enough retention time, for any reason, the raw leachate's buffering capacity is not removed and almost no benefit is gained by the biologically treated leachate. Some days there will be good floc in the flash floc tank, while other days no floc is created. In an attempt to overcome the aforementioned problems in order to treat the customer's leachate in a limited footprint, it is required to pretreat the dissolved ions in solution by removing some of them in a coagulation flocculation and sedimentation tank. By reducing the settling time of the insoluble solids the settling tanks could be reduced in size to fit inside the 20 foot shipping container. Therefore, there are several disadvantages including, but not limited to, increased complexity and steps, costs and processing time.
Accordingly, there exists a need for a leachate treating system and method for treating wastewater and/or landfill leachate that is more efficient and cost effective and allows for the benefit of a smaller processing footprint without limiting treatment effectiveness.